In New York City, $2 is what you spend for a ticket on the subway or to buy a coffee. But for billions of people around the world, $2 or less is the average amount of money you have to put food on the table every day, pay medical bills, keep children in school, and seize business opportunities. It seems impossible.

Foreign aid experts, policy makers, and even celebrities have a lot to say about the population living on $1 or $2 a day. The group we don’t often hear from is the poor themselves. As a result, most of us have little clue about how the poor manage to live on so little—so we fall back on our guesses and assumptions, and that then informs the way we think about foreign aid.

A few years ago, my colleagues Daryl Collins, Stuart Rutherford and Orlanda Ruthven set out to learn how poor families in Bangladesh, India and South Africa really manage to live on so little. Research teams spent a year getting to know families and recording their challenges, ambitions, strategies, failures, and successes.

Our new book, Portfolios of the Poor: How the World’s Poor Live on $2 a Day, comes to conclusions that turn common assumptions upside down. Far from living hand-to-mouth, all of the families interviewed were borrowing, saving, and leading active financial lives because of their poverty, not in spite of it. One of the central conclusions is that when you live on so little and face a life of uncertainty, thinking about the future is an imperative, not a luxury. You can’t afford not to save.

Some of the families have access to formal bank accounts, but most make due with imperfect financial tools of their own creation that help them deal with irregular, unpredictable incomes. Some of the most interesting strategies involve ways to save. To overcome temptation, the families create tools with built-in self-discipline features, like rule-bound savings clubs involving a few friends that shift money into a “hands-off” account; deposit collectors who come around the village daily to collect a penny or two each day; and friends delegated to be “money guards” who act like beefed-up piggy banks by restricting access to cash.

“Portfolios of the Poor” highlights that the often-hidden challenge of living on $1 or $2 a day is that these figures are just averages—some days the families earned more and some days much less. Coping with the unpredictability of income is a fundamental challenge—and it’s missed in the articulation of the United Nations’ much-discussed “Millennium Development Goals”. A better picture of poverty is captured by what we call the “triple whammy” of poverty: (1) low incomes, (2) irregular and unpredictable incomes, and (3) a lack of financial tools. Better financial tools would allow poor families to squeeze the most out of what they have.

“Portfolios of the Poor” includes concrete ideas for moving forward. Getting there, though, requires us to first step back and listen.